General Diseases 



25 



Truck crops: asparagus, bean, carrot, celery, cucumber, 

 eggplant, garden beet, garden pea, Irish potato, lettuce, 

 muskmelon, okra, onion, pepper, salsify, spinach, straw- 

 berry, tomato. Woody plants: almond, catalpa, cherry, 

 European elm, fig. Old World grapevine, mulberry, peach, 

 pecan, Persian walnut^ weeping willow. 



Fig. 6. — Root-knot (nematode) on salsify. 

 Original. 



In limited areas soil disinfection (p. 460) may be em- 

 ployed. Thorough cultivation and fertilization induces the 

 roots of perennials to extend deeper into the soil, thus reach- 

 ing below the nematode zone, affording at least temporary 

 alleviation. Three years of rotation with non-susceptible 

 crops as corn, timothy, red-top, velvet beans, resistant 

 cowpeas, barley, winter rye, or oats with care to keep down 

 susceptible weeds largely reduces the amount of soil infection. 



